Microscopic Viscoelasticity of Polymer Solutions and
Gels Observed from Translation and Rotation of Anisotropic Colloid
Probes

Published on 2018-11-08T18:37:09Z (GMT)
by

We
probe the mechanics of two different viscoelastic complex systems
at a microscopic length scale. The first is made of cross-linked polymer
gel, and the second consists of a polysaccharide solution, in which
spherical birefringent colloidal tracers have been embedded. This
method is widely known as optical microrheology. In the present work
we focus on both the translational and the rotational motions of the
tracers. The significant discrepancies observed between the results
obtained by translational and rotational microrheology imply that
the two types of motion probe the mechanical response of the matrix
in different ways. We also suggest a simplified theoretical model
to explain the experimentally observed discrepancies in terms of the
relationship between the viscoelastic moduli obtained from rotational
and translational tracer dynamics. Our results have implications for
the insights obtainable by rotational and translational microrheology
and for the role of compressibility.